Turkey’s twin earthquakes were the most powerful in recorded history – study

The Feb. 6 earthquakes that shook Turkey and Syria were probably the strongest doublet to ever occur on earth anywhere in the world, according to new research released by Chinese scientists. Moreover, the first earthquake seems to correspond to the largest earthquake that has ever hit Turkey.

According to research, the first main shock occurred around 4:18 a.m. local time and had a moment magnitude (Mw) of 7.95. About nine hours later, a second earthquake struck in the north, with a Mw of about 7.86.

“It corresponds to one of the largest earthquakes in more than 2,000 years of Turkish history,” said Xiaodong Song, president of the SinoProbe laboratory at the School of Earth and Space Sciences of the University. Peking University, who led the research published this week in the journal Earthquake Science.

Both estimates are higher than other published results.

A doublet occurs when two or more large earthquakes occur in close proximity with short intervals of time. These events occur occasionally in subduction zones and rarely on the mainland, Song explained in an interview with the Jerusalem Post Office.

General view of rubble and damage following a deadly earthquake, in Hatay, Turkey, February 15, 2023. (Credit: CLODAGH KILCOYNE/REUTERS)

He cited several earlier events in Turkey, including an event in 1688 on the North Anatolia Fault which was determined in the literature to weigh in at a magnitude of around 8.0. However, he said that “there were no good assessment records at the time to accurately determine the magnitude”.

There was also a large earthquake in 1939 in Erzincan with an estimated moment magnitude of 7.8.

Magnitude is a fundamental parameter for measuring the power of earthquakes and is of great interest to scientific research and the general public, Song said. However, there are often discrepancies when it comes to measuring earthquakes.

In the case of these February events, the magnitude results were reported with significant discrepancies. Even the difference in magnitude between the first and the second earthquake appeared very uncertain, ranging between 0.1 and 0.4.

Song’s team aimed to fill this gap by using a new and reliable long-period coded moment magnitude method to measure the size of the two events.

“The method is specifically designed for large earthquakes (MW > 7.5), and the results are little affected by source complexity and propagation effects,” said first author, Ph.D. Peking University. student Xinyu Jiang explained. “With hours of coda data over long periods, the method can produce robust momentum amplitude without further corrections.”

Since the end of his last article, Song said his research group has been collaborating with other groups to determine why such powerful earthquakes are happening now and if there might be a way to predict such events in the future. ‘coming.

What causes these earthquakes and who is at risk?

Turkey, he said, lies at the junction of several major tectonic plates: Africa, Anatolia, Arabia and Eurasia, which is why the country is prone to major earthquakes. earth. However, in most previous events, ruptures have only occurred along a fault segment. This time, several segments were broken, and the rupture rate was faster (a so-called “super-shear” rupture) in several segments than in a typical rupture.

“In this case, we believe multiple locations ruptured with super-shear velocity and triggered additional ruptures,” Song told the Job. “This super-shear failure has to do with the accumulated stress along different fault segments. The details of the triggering process are still being worked out. In addition, the super-shear failure also generated strong ground shaking over a larger area, which may explain the heavy damage from the doublet events.”

Song warned that Israel is also located along fault lines and could be vulnerable. The simultaneous rupture of several fault segments could occur to generate a larger event. In addition, he said that external factors could affect the occurrence of earthquakes, especially water, which other studies have found can alter fault behavior.

“But the main cause of earthquakes is the interaction between different plates,” Song explained. “There are several major plates beneath the Earth’s surface, and they are moving relative to each other, constantly adapting to tectonic forces. So sometimes when stress builds up beyond a limit , he must be released.”

He added that scientists are “still a long way from predicting a big earthquake”, but “there is a lot we can do” to help reduce the dangerous and deadly impact of such events.

Damage caused by the earthquake in Syria (credit: Wikimedia Commons)

For example, Song said countries like Turkey and Israel should immediately invest in strengthening structures and “preparing people so they know what to do if an earthquake happens. It can make a huge difference in terms of earthquake risk mitigation.

Finally, he recommended that earthquake-prone countries do a better job of collaborating and sharing best research and practices.

“The best way to cope is another lesson we can learn from each other,” he said.

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